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DavidT wrote:
> jdach wrote:
>
> No - I asked about the transmission rate in the Horsburgh paper
> (Concordance of polymerase chain reaction with human immunodeficiency
> virus antibody detection. J Infect Dis. 1990 Aug;162(2):542-5) which is
> the one you previously cited in evidence as showing minimal
> heterosexual transmission
>
> David:> > 2. Have you actually read these papers?
>
> Reply from David: Well, have you read the ones I actually asked about,
> specifically the Horsburgh paper above on PCR concordance? If you have
> you can easily quote the HIV seroconversion rate, surely?
>
> David replies: That doesn't answer my question.
>
> David: That doesn't answer my question. I asked if you accepted that
> studies on serodiscordant couples are affected by selection bias.
>
> For what it is worth, I agree HIV is not easily transmitted through
> heterosexual intercourse. However it IS transmitted, and transmission
> rates are demonstrably higher when HIV load is high (as is the case in
> the first few months after HIV acquisition) and if there are cofactors
> such as concommitant genital ulceration/STIs.
drdach replies:
However, I don't think selection bias is an issue for this question,
since transmission rates have been studied multiple times and found to
be about 1 per thousand sexual contacts. However, if you have any
further information you would like to share about selection bias,
please do so.
Thank you for finally admitting that HIV is not easily transmitted
within heterosexual couples.
We can go further with the discussion:
We know from HIV testing of military recruits that the incidence of an
HIV positive test in the general population is approx. 4 per thousand.
This is public domain data.
Assuming random heterosexual contacts in this population, it is easy to
calculate the number of sexual contacts needed for HIV transmission and
sero-conversion for the average person.
On the average, 250 different sexual contacts within the general
population will be required to find the one HIV positive person who
could then transmit the HIV virus. Assuming a monogamous relationship
with this HIV positive person, 1000 sexual contact with that one person
would then be needed for HIV transmission. However, if there is a
continuation of unprotected sexual contacts throughout the general
population, then 250 x 1000 would be the calculated number of sexual
contacts. This requires 250,000 different sexual contacts. This
explains why heterosexual transmission of HIV in the general population
is quite rare. It is far more likely that our hypothetical sexually
adventurous individual would have multiple recurring garden variety
nasty STD's with their consequences for many years before HIV
seroconversion. Thhis also explains why no heterosexual epidemic has
materials after 20 years of dire predictions.
The numbers change of course for high risk populations where many of
the sexual partners are HIV positive. For example if our hypothetical
adventurous person has sex with 300 people per year (one a day) and all
these people are HIV positive, then one could calculate sero-conversion
within three years. Of course, other factors such as co-existing STD's
may accelerate this time table.
So this then brings us to a discussion the question of how is it that
0.4 per cent (4 per thousand) of the general population is HIV positive
if heterosexual transmission is so difficult - it would require 250,000
different sexual contacts? How did these 0.4 percent or 1 million
people in the general population get to be HIV positive? The obvious
possible answer is via maternal - fetal transmission. They received
the HIV from their mothers.
For readers who would like more discussion of this issue, please reply
to my contact page on my web site www.drdach.com
Here is direct quote from Horsburg's article from an AIDS conference
which provides a reference for the 1 per thousand number. This is the
article you are asking about and here is the quote which you can read
for yourself.
Longini IM Jr., Clark WS, Haber M and Horsburgh CR. The stages of
HIV-1
infection, ... heterosexual HIV-1 transmission. J Infect Dis
1990,161:833-877
"The probability of transmission of HIV-1 from male to female during
an
episode of intercourse has been examined in seven studies. Analysis of
data from North American and European studies of heterosexual couples
provide estimates of per-sex-act HIV-1 transmission of approximately 1
in 1000 (0.001, ranging from 0.0008 to 0.002)."
http://www.retroconference.org/2001/posters/222.pdf
regards from www.drdach.com
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